Pulsed Gas Discharge Research Articles

Characteristics of a quasi-stationary non-self-sustained pulsed gas discharge with a hot cathode

The paper presents the electrode system and main characteristics of a non-selfsustained pulsed discharge with a hot cathode operating in argon at a pulse repetition frequency of 5 kHz and pulse duration of 50 ps. It is found that during the operation at a pressure of 0.3 Pa, the discharge current can reach amplitudes of up to 300 A and more with a rather high average discharge current of ∼ 100 A and low average discharge operating voltage of less than 20 V. The ion current from the discharge plasma to a Langmuir probe oscillates at frequency of about 100 kHz.

1D simulation of runaway electrons generation in pulsed high-pressure gas discharge

The results of theoretical modelling of runaway electron generation in the high-pressure nanosecond pulsed gas discharge are presented. A novel hybrid model of gas discharge has been successfully built. Hydrodynamic and kinetic approaches are used simultaneously to describe the dynamics of different components of low-temperature discharge plasma. To consider motion of ions and low-energy (plasma) electrons the corresponding equations of continuity with drift-diffusion approximation are used. To describe high-energy (runaway) electrons the Boltzmann kinetic equation is included. As a result of the simulation we obtained spatial and temporal distributions of charged particles and electric field in a pulsed discharge. Furthermore, the energy spectra calculated runaway electrons in different cross-sections, particularly, the discharge gap in the anode plane. It is shown that the average energy of fast electrons (in eV) in the anode plane is usually slightly higher than the instantaneous value of the applied voltage to the gap (in V).

Production and simultaneous deposition of ultradisperse particles on a substrate in a pulsed atmospheric-pressure gas discharge traveling over the surface of electrodes in the self-magnetic field

A method of production and simultaneous deposition of ultradisperse particles is described. In this method, a metal is melted and sprayed in a high-power pulsed arc discharge traveling over the surface of electrodes in the self-magnetic field. The discharge is initiated in air or an inert gas at atmospheric or low pressure. An experimental setup intended for this method provides a power density on the cathode of 108–1010 W/cm2. Such values are comparable to those obtained in a vacuum arc or with pulsed laser radiation. Ultradisperse catalytic particles deposited by this method on the polymer membranes of hydrogen fuel cells are several nanometers across and offer a high adhesion to the membrane.

A time scale for electrical screening in pulsed gas discharges

The Maxwell time is a typical time scale for the screening of an electric field in a medium with a given conductivity. We introduce a generalization of the Maxwell time that is valid for gas discharges: the ionization screening time, that takes the growth of the conductivity due to impact ionization into account. We present an analytic estimate for this time scale, assuming a planar geometry, and evaluate its accuracy by comparing with one- and three-dimensional numerical simulations. We investigate the minimum plasma density required to prevent the growth of streamers with local field enhancement, and we discuss the effects of photoionization and electron detachment on ionization screening. Our results can help to understand the development of pulsed discharges, for example nanosecond pulsed discharges at atmospheric pressure or halo discharges in the lower ionosphere.

Method for measuring the absorbed energy in nanosecond electric discharges

A method for measuring the energy absorbed under a nonlinear load that employs a reverse current shunt is described. The design features of the reverse current shunt and the peculiarities of its use to study high-voltage (10–100 kV) pulses with a nanosecond duration are considered. The experimental results of applying this method to the investigation of the energy absorption during high-voltage pulse gas discharge are presented.

Dynamics of shock waves appearing during pulsed high-current electric gas discharges. II. Regular polygonal shock waves with closed surface fronts

Dynamics of regular polygonal shock waves (SWs), generated at thin wire explosion, with a closed surface front and numbers of sides n = 3, 4, 5, 6, 8, 10, 12, and 16 in the plane of polygons is experimentally studied. Depending on the initial Mach number MPSW0 of such waves and the number n, two convergence modes are implemented: convergence with and without changes in the number of sides n. It is shown that the shape of the reflected wave front differs from the shape of the converging SW front for polygonal SWs with n ≥ 8, i.e., it becomes smooth. The number MPSW0 is determined depending on initial characteristics of an SW generator and gas. A significant amplification of such SWs with n ≥ 12 is observed near to the center of polygons; their maximum amplification is estimated.

Pulsed Chemical Oxygen Iodine Lasers Excited by Pulse Gas Discharge with the Assistance of Surface Sliding Discharge Pre-ionization

Continuous-wave chemical oxygen-iodine lasers (COILs) can be operated in a pulsed operation mode to obtain a higher peak power. The key point is to obtain a uniform and stable glow discharge in the mixture of singlet delta oxygen and iodide. We propose using an electrode system with the assistance of surface sliding pre-ionization to solve the problem of the stable glow discharge with a large aperture. The pre-ionization unit is symmetrically fixed on the plane of the cathode surface. A uniform and stable glow discharge is obtained in a mixture of iodide (such as CH3I) and nitrogen at the specific deposition energy of 4.5 J/L, pressure of 1.99–3.32 kPa, aperture size of 11 cm × 10 cm. The electrode system is applied in a pulsed COIL. Laser energy up to 4.4 J is obtained and the specific energy output is 2 J/L.

ADAPTIVE TIME SPLITTING METHOD FOR MULTI-SCALE EVOLUTIONARY PARTIAL DIFFERENTIAL EQUATIONS

This paper introduces an adaptive time splitting technique for the solution of stiff evolutionary PDEs that guarantees an effective error control of the simulation, independent of the fastest physical time scale for highly unsteady problems. The strategy considers a second order Strang method and another lower order embedded splitting scheme that takes into account potential loss of order due to the stiffness featured by time-space multi-scale phenomena. The scheme is then built upon a precise numerical analysis of the method and a complementary numerical procedure, conceived to overcome classical restrictions of adaptive time stepping schemes based on lower order embedded methods, whenever asymptotic estimates fail to predict the dynamics of the problem. The performance of the method in terms of control of integration errors is evaluated by numerical simulations of stiff propagating waves coming from nonlinear chemical dynamics models as well as highly multi-scale nanosecond repetitively pulsed gas discharges, which allow to illustrate the method capabilities to consistently describe a broad spectrum of time scales and different physical scenarios for consecutive discharge/post-discharge phases.

Pulse Operation of Chemical Oxygen-Iodine Laser by Pulsed Gas Discharge with the Assistance of Spark Pre-ionization

The continuous wavelength chemical oxygen-iodine laser can be turned into pulse operation mode in order to obtain high energy and high pulse power. We propose an approach to produce iodine atoms instantaneously by pulsed gas discharge with the assistance of spark pre-ionization to achieve the pulsed goal. The influence of spark pre-ionization on discharge homogeneity is discussed. Voltage-current characteristics are shown and discussed in existence of the pre-ionization capacitor and peaking capacitor. The spark pre-ionization and peaking capacitor are very helpful in obtaining a stable and homogeneous discharge. The lasing is achieved at the total pressure of 2.2–2.9kPa and single pulse energy is up to 180 mJ, the corresponding specific output energy is 1.0 J/L.

Intracavity absorption and emission spectroscopy of atoms in pulsed gas discharges

Absorption and emission spectra of U and Na atoms in the 590-nm spectral range were studied experimentally using pulsed hollow-cathode gas discharges. The spectra were recorded with a high-sensitivity intracavity laser spectrometer. The possibility of generating coherent emission on atomic emission lines in gas-discharge plasmas was demonstrated experimentally.

Formation of the distribution function for runaway electrons in strong fields of pulsed gas discharges

A simplified Boltzmann equation describing the escape of electrons in a weakly ionized gas is constructed. The electric fields are assumed to be so strong that all electrons are runaway electrons and the electron distribution function is strongly anisotropic. The equation is solved analytically, and it is shown that the electron density in relatively weak fields exponentially increases with time, while the momentum dependence of the distribution function exponentially decreases. In strong fields, the electron density increases with time logarithmically and the momentum dependence of the electron distribution function is nonmonotonic. The characteristic scales of time and energy, which determine different scenarios, are obtained.

Repetitive Pulsed High-Voltage Generator Using Semiconductor Opening Switch for Atmospheric Discharge

Atmospheric pulsed gas discharge requires very short duration high-voltage pulse delivered to the electrodes. Moreover, atmospheric gas discharge of very short pulse is usually a high impedance load. Pulsed power technology based on inductive energy storage (IES) is suitable for this application. In this paper, we present a repetitive pulsed high-voltage generator with IES. It uses semiconductor opening switch, combined with magnetic switches and insulated-gate bipolar transistors. Experimental tests were carried out with 30-cm-long plate-to-knife discharge load. An output voltage of ~ 50 kV with a pulse duration of ~10 ns was obtained for a gap distance of 1 cm in air. The generator has been operated at a repetition rate up to 250 Hz. Uniform discharge plasma has been identified.

Soft x-ray emission from a pulsed gas discharge in a pseudosparklike electrode geometry

The mechanism of the soft x-ray generation in a pulsed high current discharge is investigated by means of time and space resolved characterization of the extreme ultraviolet emitting regions and discussion of the related electrical circuit parameters. The plasma is ignited in a pseudosparklike electrode geometry. In a discharge of 15 J, stored electrical energy characteristic emission of different gases (oxygen, argon, and nitrogen) is excited in the spectral range from 2 to 5 nm. Special interest is devoted to the 2.88 nm line emission of heliumlike nitrogen ions within the spectral range of the water window to be used for x-ray microscopy. For the nitrogen discharge, an admixture of xenon leads to axial shorter plasma emission as well as to a smaller diameter below 300 μm of the short wavelength emission. Investigation of the xenon related emission in the range of 10–16 nm indicates that radiative cooling is a possible reason for the observed decrease in the radius. Time and spatial resolved images show that the x-ray emission exhibits an axial dynamic in addition to the usual compression occurring in pinch plasmas.

Effect of High-Voltage Pulsed Discharges on Deflagration to Detonation Transition

An experimental sutdy of ignition and detonation initiation by two different kinds of high-voltage pulsed gas discharge has been performed in two smooth detonation tubes. The experiments were carried out at pressures ranging from 0.15 to 1 bar in various gaseous stoichiometric mixtures. In the first setup, a distributed nonequilibrium nanosecond discharge was used for mixture excitation and ignition. In the second setup, a localized microsecond pulsed spark discharge with a stored energy of 14 J developed. The electrical parameters of the discharges, ignition delay time, flame front, and shock wave velocities were measured in the experiments. ...

Repetitive Pulsed High Voltage Generation Using Inductive Energy Storage with Static-induction Thyristor as Opening Switch

A compact pulsed high-voltage generator has been developed for applications in pulsed gas discharges. Its operation principle is based on inductive energy storage and it uses a static induction thyristor as the opening switch. It is capable of generating pulsed high voltage of ~15 kV with pulse width of ~200 ns for load resistance of 1 kOmega. This generator can be operated at repetition rate as high as 50 kHz if it is driven directly by 200 V power supply and is cooled by transformer oil. It can also be driven by a 12 V car battery through a chopper circuit, while operating at repetition rate of 2 kHz. In this case, an overall energy efficiency of ~40 % has been obtained.

Pulsed discharge in a hollow cathode with the detection of ions in a time-of-flight mass spectrometer: Analytical capabilities in the analysis of solid samples

The results of a study of a new analytical system that includes an ion source with a hollow-cathode pulsed gas discharge and a time-of-flight mass spectrometer are reported. It was found that such a system can be successfully used for the direct analysis of metal and dielectric solid samples. The results of the optimization of various ionizer parameters, such as the delay of an ejecting pulse with respect to a discharge pulse and the bias voltage of the anode-cathode pair, are given. It was proposed to use an additive of hydrogen as a reaction gas for a considerable decrease in the intensities of gas components in the mass spectrum, and the effectiveness of this approach was demonstrated. The possibility of the rapid and efficient direct analysis of solid samples with the use of a hollow-cathode pulsed glow discharge was demonstrated using an example of the analysis of high-purity copper samples and the glassy slag of molten lead.

On a source of outgoing electrons in a pulsed gas discharge

It has been shown that explosive electron emission is delayed by 10−10 s with respect to field emission in a pulsed subnanosecond discharge in atmospheric air. A pulse of outgoing electrons is observed for approximately the same time in air. Correspondingly, field emission is a source of these electrons. Owing to the sharp nonlinearity of the emission current density as a function of the electric field j(E), the real duration of the current pulse of the outgoing electrons is equal to about 10−11 s.

Pulsed population inversion in recombination of positive metal ions with negative oxygen ion

We discuss the ion-ion recombination of positive metal ions and negative oxygen ion in a pulsed gas discharge for realization of the pulsed inversion population mechanism. The metal atom energy levels most populated in this process are estimated. The energy level diagrams with probable transitions for several metal atoms are presented.

Ignition of Propane–Air Mixtures by a Repetitively Pulsed Nanosecond Discharge

Results of an experimental study of the efficiency of the ignition of propane-air mixtures by a high voltage repetitively pulsed nanosecond gas discharge (10 kV, 10 ns, 30 kHz) are presented for the pressure range 0.35-2.0 bar. The measured minimal energy for ignition is found to decrease with the pressure. A significant reduction of the ignition delay and a decrease of the overall combustion duration were obtained by using a train of high-voltage pulses. Spectroscopic measurements in a 1-bar air just after a 10-pulse train (300 mus) of about 10 mJ in total energy show the presence of N, N+, O, and O+ atomic species and a gas temperature increase up to 3000 K

On the similarity law in picosecond gas discharges

It has been shown that the product of the gas pressure p and the discharge formation time τ is unambiguously related to the reduced electric-field strength E/p for air and argon in the picosecond range of τ. This dependence was previously found for the nanosecond range. The available experimental data are satisfactorily explained in the framework of the theory of the multielectron initiation of pulsed gas discharges that was proposed in my previous works.